Chapter 9 Wood Copyright 2009 Delmar Cengage Learning

Chapter 9 Wood Copyright © 2009 Delmar, Cengage Learning

Objectives • Correctly identify the differences between hardwood and softwood trees • Discuss the processing of the wood from tree to board in sequential order • Name and describe common lumber defects • Describe how the production and sale of hardwood and softwood lumber differs Copyright © 2009 Delmar, Cengage Learning

Objectives (continued) • Calculate board feet • Identify different types of grain and explain how they affect the appearance of wood • Describe wood movement and how it affects woodworking practices • Identify sources for acquiring wood Copyright © 2009 Delmar, Cengage Learning

Introduction • Trees are a source of abundant materials • Virtually every part of the tree can be turned to our use • Trees provide the materials used to build and furnish our homes Copyright © 2009 Delmar, Cengage Learning

Hardwoods and Softwoods • Trees can be divided into two main categories: – Hardwoods (deciduous) – Softwoods (coniferous) • Parts of a tree – – Pith Annual rings Bark Cambium: has two parts—phloem and xylem Copyright © 2009 Delmar, Cengage Learning

Hardwoods and Softwoods (continued) • Parts of a tree (continued) – Sapwood – Heartwood – Medullary rays Copyright © 2009 Delmar, Cengage Learning

sapwood heartwood sapwood Figure 9 -3 Both walnut (top) and cherry (bottom) exhibit a striking difference in color between their heartwood and sapwood. Copyright © 2009 Delmar, Cengage Learning

From the Forest to the Shop • Foresters and loggers select trees to be cut for lumber • Trees are cut down and their limbs are removed • Trunks are bundled together and transported to a sawmill for processing • At the mill, logs are sorted by species Copyright © 2009 Delmar, Cengage Learning

From the Forest to the Shop (continued) • Best logs are set aside to be processed into cabinet-grade veneer • Bark is stripped off by a debarking machine • Logs go through metal detector to sort out logs containing metal • Majority of logs that are processed into lumber are squared up – Squared-up log is called cant Copyright © 2009 Delmar, Cengage Learning

From the Forest to the Shop (continued) • Cants are sawn into boards • Edges of boards are trimmed to achieve uniform width; boards are cut to length • Boards go to the grader to be sorted • After grading, boards are packaged for drying Copyright © 2009 Delmar, Cengage Learning

Figure 9 -11 Plainsawn and quartersawn lumber have a very different appearance. Copyright © 2009 Delmar, Cengage Learning

From the Forest to the Shop (continued) • After drying, we have roughsawn lumber • Depending on the tools a shop has, it may purchase roughsawn lumber • Lumber not sold as roughsawn is surfaced • Most of the lumber purchased by cabinetmakers is surfaced two sides (S 2 S) Copyright © 2009 Delmar, Cengage Learning

Lumber Defects • Common natural defects – – Knot Blue stain Pitch pocket Bark pocket Copyright © 2009 Delmar, Cengage Learning

Lumber Defects (continued) • Defects that occur in milling and drying – – – – Warp Bow Crook Cup Twist Kink Wane Copyright © 2009 Delmar, Cengage Learning

Lumber Defects (continued) • Defects that occur in milling and drying (continued) – – – Split Check Shake Case hardening Honeycombing Copyright © 2009 Delmar, Cengage Learning

Lumber Grades • Softwood grades – Based on standards set by associations of lumber producers – Must conform to U. S. Department of Commerce American Lumber Standards – Based on structural integrity of a board Copyright © 2009 Delmar, Cengage Learning

Lumber Grades (continued) • Hardwood grades – Standards established by National Hardwood Lumber Association (NHLA) – Based on the amount of clear wood that can be cut from each board Copyright © 2009 Delmar, Cengage Learning

Estimating and Purchasing Lumber • Softwood lumber – Sold in standard thicknesses, widths, and lengths – Ordered by its nominal size – Sold by the individual piece Copyright © 2009 Delmar, Cengage Learning

Estimating and Purchasing Lumber (continued) • Hardwood lumber – Estimated and sold by the board foot, rather than by the piece – Widths and lengths are not standardized – Thickness of the piece is indicated by the quarter of an inch, and not in whole inches Copyright © 2009 Delmar, Cengage Learning

Grain • Strength of any wooden component is determined by its grain and how that grain is oriented on the furniture component • Also affects stability of the material, gluing properties, and finishing • Types of grain – End grain, longitudinal grain, edge grain, face grain, radial grain, and tangential grain Copyright © 2009 Delmar, Cengage Learning

Figure 9 -26 A board exhibiting radial grain on its face was cut along a radius running from the center of the tree outward. Copyright © 2009 Delmar, Cengage Learning

Figure 9 -28 A board showing tangential grain on its face was cut tangent to the growth rings of the tree. Copyright © 2009 Delmar, Cengage Learning

Grain (continued) • Wood movement – Wood is not a static material • Expands and contracts in response to changes in relative humidity – As we build furniture, we have to allow for this movement – The way wood moves is directly related to its grain • Greatest amount of movement takes place tangent to the grain Copyright © 2009 Delmar, Cengage Learning

Sources of Wood • • Home centers Retail lumber stores Hardwood mills Can have trees of your own cut and milled by a portable band saw mill Copyright © 2009 Delmar, Cengage Learning

Sources of Wood (continued) • • Structures slated for demolition Local road crews Power companies Mail order and online Copyright © 2009 Delmar, Cengage Learning

Summary • Wood is a beautiful yet complex material • Understanding how wood grew and was milled and seasoned gives us vital tools for working with it successfully • Appearance of wood and its behavior relative to the surrounding environment are largely determined by the roles the wood played in the original tree Copyright © 2009 Delmar, Cengage Learning